Hitachi Construction Machinery Co., Ltd.

Kuniaki Yoshida

Toichi Hirata

Genroku Sugiyama

Hideaki Tanaka

Masakazu Haga

Yasuo Tanaka

Hiroshi Watanabe

Eiki Izumi

Akira Tatsumi

Nobuya Okabe

Ichiro Hirami

Shinichi Mihara

Hydraulic driving method of and hydraulic driving apparatus for

Control system for a load-sensing hydraulic drive circuit comprising; at least one hydraulic pump; hydraulic actuators driven by the hydraulic pump; and a pressure compensated flow control valve between the pump and each of the actuators, for controlling a flow rate of fluid to each actuator in response to a control signal. The control system has first detection means for detecting a differential pressure between the pump delivery pressure and the maximum load pressure; second detection means for detecting the pump delivery pressure; first means for calculating a differential pressure target pump delivery amount Q.DELTA.p to hold the differential pressure constant; second means for calculating an input limiting target pump delivery amount QT based on at least a pressure signal from the second detection means and an input limiting pump function; third means for selecting one of the differential pressure target delivery amount Q.DELTA.p and the input limiting target delivery amount QT as a pump delivery amount target value Qo, and then controlling the pump delivery amount to not exceed the input amount QT; and fourth means for calculating a compensation value Qns to limit a total consumable actuator flow rate based on at least the input amount QT and the differential pressure target delivery amount Q.DELTA.p when the input amount QT is selected by the third means, and then controlling the pressure compensated flow control valve based on the compensation valve Qns.

Control system for load-sensing hydraulic drive circuit

A drive control system, which is suitable for use in a hydraulic machine, is equipped with an electric lever device having a manipulation lever and a potentiometer for generating an electrical manipulation signal corresponding to the degree of each manipulation of the lever, a control valve connected to a hydraulic circuit adapted to actuate a hydraulic actuator, and a controller unit equipped with a main controller for receiving the manipulation signal and computing a control signal for the control valve on the basis of the manipulation signal and an output device for generating an electrical actuation signal corresponding to the control signal. The system also includes a neutral position sensing means provided with the electric lever device and adapted to sense a neutral position of the manipulation lever and an inhibition device which receives an output signal from the neutral position sensing means and when the manipulation lever is at the neutral position, inhibits the transmission of a signal between the main controller of the control means and the control valve.

Drive control system for hydraulic machine

The brake circuit apparatus for a hydraulic motor in a hydraulic circuit system having at least one main hydraulic pump, a hydraulic motor driven by a hydraulic fluid supplied from the main pump and having a rotary shaft, and a directional control valve actuated by an operation device for control of flow rate and flow direction of the hydraulic fluid supplied to the hydraulic motor from the main pump. The hydraulic motor is provided with a mechanical brake device having a brake release cylinder adapted to release the rotary shaft of the motor from the braking by the mechanical brake device by supply of a hydraulic fluid to the brake release cylinder. The apparatus further has an auxiliary hydraulic pump and a control circuit connected to the auxiliary pump, brake release cylinder and reservoir for control of fluid communication therebetween. The control circuit includes a hydraulic fluid supply line for receiving a hydraulic fluid supplied from the auxiliary hydraulic pump, a first line connected between the hydraulic fluid supply line and the brake release cylinder, and a second line connected between the hydraulic fluid supply line and the reservoir.

Brake circuit apparatus for hydraulic motor

A control system for a hydraulic excavator having a prime mover, revolution number control device for the prime mover, at least one variable displacement hydraulic pump driven by the prime mover, displacement volume control device for the pump, actuators driven by pressurized fluid discharged from the pump and working elements driven by the respective actuators. The control system includes maximum revolution number altering device for the prime mover associated with the revolution number control device, maximum displacement volume altering device for the pump associated with the displacement volume control devices, devices for sensing the operation condition of the actuators, devices for selecting an operation mode for each working element and control devices. The maximum revolution number altering device provides at least one maximum revolution number of the prime mover and the maximum displacement volume altering device provides at least one maximum displacement volume so that maximum revolution numbers of the prime mover and maximum displacement volumes are arranged in a plurality of combinations. The plurality of combinations are set in association with the operation condition of the actuators and the selection of the operation mode. The control means selects a combination of the maximum revolution number of the prime mover and the maximum displacement volume of the pumps on basis of output signals of the sensors and selection devices and drives the maximum revolution number altering device and the maximum displacement volume altering device to set the maximum revolution number of the prime mover and the maximum displacement volume of the hydraulic pump.

Control system for hydraulically-operated construction machinery

Growing community of inventors

Tsuchiura, Japan

Kuniaki Yoshida